The integrated control of cardiovascular homeostasis is achieved through a combination of both direct neuronal control and systemic neurohormonal activation. Although the resultant release of both contractile and relaxant factors is normally under stringent regulation, an aberration in this status quo can result in cardiohemodynamic dysfunction with pathological consequences.
The principal mammalian vasoactive factors that comprise this neurohumoral axis are angiotensin-II, endothelin-1, and norepinephrine, all of which function via an interaction with specific G-protein coupled receptors (GPCR). Urotensin-II, represents an important member of this neurohumoral axis.
In the fish, this peptide has significant hemodynamic and endocrine actions in diverse end-organ systems and tissues:
both vascular and non-vascular (smooth muscle contraction) including smooth muscle preparations from the gastrointestinal tract and genitourinary tract. Both pressor and depressor activity has been described upon systemic administration of exogenous peptide.
osmoregulation effects which include the modulation of transepithelial ion (Na+, Cl−) transport.
Although a diuretic effect has been described, such an effect is postulated to be secondary to direct renovascular effects (elevated GFR); urotensin-II influences prolactic secretion and exhibits a lipolytic effect in fish (activating triacylglycerol lipase resulting in the mobilization of non-esterified free fatty acids) (Person, et al. Proc. Natl. Acad. Sci. (U.S.A.) 1980, 77, 5021; Conlon, et al. J. Exp. Zool. 1996, 275, 226); human urotensin-II has been found to be an extremely potent and efficacious vasoconstrictor; exhibited sustained contractile activity that was extremely resistant to wash out; and had detrimental effects on cardiac performance (myocardial contractility). Human urotensin-II was assessed for contractile activity in the rat-isolated aorta and was shown to be a very potent contractile agonist. Based on the in vitro pharmacology and in vivo hemodynamic profile of human urotensin-II, it plays a pathological role in cardiovascular diseases characterized by excessive or abnormal vasoconstriction and myocardial dysfunction. (Ames et al. Nature 1990, 401, 282.)
Compounds that antagonize the urotensin-II receptor may be useful in the treatment of congestive heart failure, stroke, ischemic heart disease (angina, myocardial ischemia), cardiac arrhythmia, hypertension (essential and pulmonary), COPD, fibrosis (e.g. pulmonary fibrosis), restenosis, atherosclerosis, dyslipidemia, asthma, neurogenic inflammation and metabolic vasculopathies all of which are characterized by abnormal vasoconstriction and/or myocardial dysfunction. Urotensin antagonists may provide end organ protection in hypersensitive cohorts in addition to lowering blood pressure.
Since urotensin-II and GPR 14 are both expressed within the mammalian CNS (Ames et al. Nature 1999, 401, 282), they also may be useful in the treatment of addiction, schizophrenia, cognitive disorders/Alzheimers disease, impulsivity, anxiety, stress, depression, pain, migraine, neuromuscular function, Parkinsons, movement disorders, sleep-wake cycle, and incentive motivation.
Functional urotensin-II receptors are expressed in rhabdomyosarcomas cell lines and therefore may have oncological indications. Urotensin may also be implicated in various metabolic diseases such as diabetes and in various gastrointestinal disorders, bone, cartilage, and joint disorders (e.g., arthritis and osteoporosis); and genito-urinary disorders. Therefore, these compounds may be useful for the prevention (treatment) of gastric reflux, gastric motility and ulcers, arthritis, osteoporosis and urinary incontinence.